1. Field of the Invention
The present invention relates to a vehicle drum brake and more particularly to a connecting construction of a strut disposed between a parking brake lever and one of brake shoes and a strut return spring for returning the strut to its initial position.
2. Description of the Related Art
As vehicle drum brakes, there are known a drum brake having a construction in which a pair of brake shoes, that is, a first brake shoe and a second brake shoe, which are disposed to face each other on an interior side of a backing plate which is fixedly attached to a vehicle body, both the brake shoes are held at a predetermined interval while distal end portions thereof are biased so as to narrow a distance therebetween by a return spring, and the distal end portions of the brake shoes are caused to move away from each other towards an inner circumferential surface of the drum brake so as to expand the distance therebetween when the brakes are applied. As parking brake mechanisms adapted to be incorporated in drum brakes like the one described above, there is a parking brake mechanism in which the movable end portion of the second shoe and one end of a parking brake lever are connected rotatably by a pivot, a pull means such as a parking brake cable or a brake rod which is pulled by an operating member such as a hand parking brake lever or a foot parking brake pedal is connected to the other end of the parking brake lever, and a parking brake actuating strut is disposed between a position which lies closer to where the pull means is connected than where the parking brake lever is connected to the second brake shoe and the movable end portion of the first brake shoe.
This strut includes a curved portion which is curved towards an outer circumferential side of the backing plate so as to avoid an interference with a member such as a hub unit disposed at the center of the backing plate at a longitudinal central portion thereof. In the strut, an engagement hole is provided in an end portion which lies closer to the second brake shoe 2 than the curved portion for a strut return spring adapted to return the strut to its initial position after it ends its operation to be brought into engagement therewith. The strut return spring is brought into engagement with the engagement hole at one end and an installation hole formed in the second brake shoe at the other end thereof (refer to JP-UM-B-7-753 and JP-A-2002-295542, for example).
In the strut described in JP-UM-B-7-753 and JP-A-2002-295542, a fitting groove where a web of the second brake shoe and the parking brake lever are fitted in a superposed state is provided in the one end portion of the strut where the engagement hole is provided. To form the engagement hole in the way described above, the one end portion of the strut has to be caused to project in the direction of an axle so as to ensure that the one end portion has a required thickness. However, the projecting amount of the one end portion in the direction of the axle has to be suppressed to as low a level as possible to avoid the enlargement of the strut, and to make this happen, it is not possible to ensure giving the one end portion an enough thickness to form therein an engagement hole like the one described above through punching by a press. Due to this, since such an engagement hole has to be formed by a cutting operation, some labor hours have to be spent forming the engagement hole, resulting in a poor productivity.